{"id":"CVE-2021-47107","title":"In the Linux kernel, the following vulnerability has been resolved:\n\nNFSD: Fix READDIR buffer overflow\n\nIf a client sends a READDIR count argument that is too small (say,\nzero), then the buffer size calculation in the new init_dirlist\nhe…","summary":"In the Linux kernel, the following vulnerability has been resolved:\n\nNFSD: Fix READDIR buffer overflow\n\nIf a client sends a READDIR count argument that is too small (say,\nzero), then the buffer size calculation in the new init_dirlist\nhe…","severity":"critical","cvss":9.8,"cvssVector":"CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:H/A:H","cwe":["CWE-120"],"vendor":"linux","product":"linux_kernel","affected":["linux_kernel >= 5.13, < 5.15.12","linux_kernel = 5.16"],"patched":["linux_kernel 5.15.12"],"published":"2024-03-04","updated":"2026-08-04","source":"NVD","sourceUrl":"https://nvd.nist.gov/vuln/detail/CVE-2021-47107","references":[{"url":"https://git.kernel.org/stable/c/53b1119a6e5028b125f431a0116ba73510d82a72","label":"416baaa9-dc9f-4396-8d5f-8c081fb06d67"},{"url":"https://git.kernel.org/stable/c/9e291a6a28d32545ed2fd959a8165144d1724df1","label":"416baaa9-dc9f-4396-8d5f-8c081fb06d67"},{"url":"https://git.kernel.org/stable/c/eabc0aab98e5218ceecd82069b0d6fdfff5ee885","label":"416baaa9-dc9f-4396-8d5f-8c081fb06d67"},{"url":"https://git.kernel.org/stable/c/53b1119a6e5028b125f431a0116ba73510d82a72","label":"af854a3a-2127-422b-91ae-364da2661108"},{"url":"https://git.kernel.org/stable/c/9e291a6a28d32545ed2fd959a8165144d1724df1","label":"af854a3a-2127-422b-91ae-364da2661108"},{"url":"https://git.kernel.org/stable/c/eabc0aab98e5218ceecd82069b0d6fdfff5ee885","label":"af854a3a-2127-422b-91ae-364da2661108"},{"url":"https://cert-portal.siemens.com/productcert/html/ssa-265688.html","label":"0b142b55-0307-4c5a-b3c9-f314f3fb7c5e"}],"tags":["nvd"],"epss":0.00847,"epssPercentile":0.56581,"ingestedAt":"2026-08-05T05:58:02.630Z","slug":"CVE-2021-47107","body":"## Overview\n\nIn the Linux kernel, the following vulnerability has been resolved:\n\nNFSD: Fix READDIR buffer overflow\n\nIf a client sends a READDIR count argument that is too small (say,\nzero), then the buffer size calculation in the new init_dirlist\nhelper functions results in an underflow, allowing the XDR stream\nfunctions to write beyond the actual buffer.\n\nThis calculation has always been suspect. NFSD has never sanity-\nchecked the READDIR count argument, but the old entry encoders\nmanaged the problem correctly.\n\nWith the commits below, entry encoding changed, exposing the\nunderflow to the pointer arithmetic in xdr_reserve_space().\n\nModern NFS clients attempt to retrieve as much data as possible\nfor each READDIR request. Also, we have no unit tests that\nexercise the behavior of READDIR at the lower bound of @count\nvalues. Thus this case was missed during testing.\n\n## Affected\n\n- `linux_kernel >= 5.13, < 5.15.12`\n- `linux_kernel = 5.16`\n\n## Remediation\n\nUpgrade past the affected range:\n\n- `linux_kernel 5.15.12`","depth":"midnight","depthScore":54,"depthScoreParts":{"impact":53.9,"likelihood":0.2,"exploitation":0,"ransomware":0},"changes":[]}